Move SD Card subsystem outside of RC2014 recipe and add protocols

Although the SPI Relay driver is RC2014-specific, the SD Card driver
is generic enough to be a subsystem. That's the second subsystem we
add and this warrants, I think, the formalization of a new concept:
protocols.

blk/001

@@ -6,10 +6,11 @@ MASTER INDEX
 160-199 unused
 200 Z80 assembler             260 Cross compilation
 280 Z80 boot code             350 Core words
-410 PS/2 keyboard subsystem   420-489 unused
+410 PS/2 keyboard subsystem   420 SD Card subsystem
+440-489 unused
 490 TRS-80 Recipe             520 Fonts
 550 TI-84+ Recipe             580 RC2014 Recipe
-620 Sega Master System Recipe
+600-619 unused                620 Sega Master System Recipe
 650 AVR assembler             690-729 unused
 730 8086 assembler
 800 8086 boot code            830 PC/AT recipe

blk/410

@@ -1,10 +1,10 @@
 PS/2 keyboard subsystem
 
-Provides (key) from a driver providing (ps2kc). That is, for a
-driver taking care of providing all key codes emanating from a
-PS/2 keyboard, this subsystem takes care of mapping those key-
-strokes to ASCII characters. This code is designed to be cross-
-compiled and loaded with drivers.
+Provides (key) from a driver providing the PS/2 protocol. That
+is, for a driver taking care of providing all key codes emanat-
+ing from a PS/2 keyboard, this subsystem takes care of mapping
+those keystrokes to ASCII characters. This code is designed to
+be cross-compiled and loaded with drivers.
 
 Requires PS2_MEM to be defined.
 

blk/420

@@ -0,0 +1,10 @@
+SD Card subsystem
+
+Load range: B423-B436
+
+This subsystem is designed for a ad-hoc adapter card that acts
+as a SPI relay between the z80 bus and the SD card. It requires
+a driver providing the SPI Relay protocol.
+
+Through that layer, this driver implements the SDC protocol
+allowing it to provide BLK@ and BLK!.

blk/580

@@ -5,4 +5,4 @@ ACIA, SD card and AT28 EEPROM.
 
 581 ACIA                       586 Zilog SIO driver
 592 AT28 EEPROM                595 SPI relay
-600 SD card                    618 Xcomp unit
+599 Xcomp unit

blk/595

@@ -7,6 +7,6 @@ the device, and writing to SPI_DATA is expected to initiate a
 byte exchange. The result of the exchange is excpected to be re-
 trieved by reading SPI_DATA.
 
-Provides (spie) (enable), (spid) (disable), (spix) (xchange).
+Provides the SPI relay protocol.
 
 Load driver with "596 LOAD".

blk/600

@@ -1,11 +0,0 @@
-SD Card driver
-
-Load range: 603-616
-
-This driver is designed for a ad-hoc adapter card that acts as a
-SPI relay between the z80 bus and the SD card. It requires a SPI
-driver providing (spix), (spie) and (spid), which oh surprise!
-is included in Collapse OS at B595.
-
-Through that layer, this driver implements the SDC protocol
-allowing it to provide BLK@ and BLK!.

doc/protocol.txt

@@ -0,0 +1,27 @@
+# Protocols
+
+Some subsystems (and in the case of KEY and EMIT, the core) re-
+quire drivers to implement certain words in a certain way. For
+example, the core requires drivers to implement (key) and (emit)
+or else it won't know how to provide a console.
+
+These protocols are described here.
+
+# TTY protocol
+
+(key)      -- c    Returns the next typed key on the console.
+                   If none, block until there is one.
+(emit)     c --    Spit a character on the console.
+
+# PS/2 protocol
+
+(ps2kc)   -- kc    Returns the next typed PS/2 keycode from the
+                   console. Blocking.
+
+# SPI Relay protocol
+
+(spie)    --       Enable SPI device
+(spid)    --       Disable SPI device
+(spix)    n -- n   Perform SPI exchange (push a number, get a
+                   number back)
+                  

recipes/rc2014/sdcard/README.md

@@ -78,10 +78,10 @@ declaring `SPI_DATA`, `SPI_CSLOW` and `SPI_CSHIGH`, which are respectively `4`,
 This driver provides `(spix)`, `(spie)` and `(spid)` which are then used in the
 SDC driver.
 
-The SDC driver is at B600. It gives you a load range. This means that what
+The SDC driver is at B420. It gives you a load range. This means that what
 you need to insert in `xcomp` will look like:
 
-    603 616 LOADR  ( sdc )
+    423 436 LOADR  ( sdc )
 
 You also need to add `BLK$` to the init sequence.
 

recipes/rc2014/xcomp.fs

@@ -1,3 +1,3 @@
-618 LOAD
+599 LOAD
 ORG @ 256 /MOD 2 PC! 2 PC!
 H@ 256 /MOD 2 PC! 2 PC!